Pneumatic percussive tool having a fluidic control valve

ABSTRACT

A pneumatically powered percussive tool having a piston hammer which is pneumatically reciprocable to pound an anvil against a work steel. Live air is fed to the piston cylinder through a fluidic valve unit. The valve unit has passages connected with opposite ends of the piston cylinder; it has no moving parts. Live inlet air entering a reaction chamber of the valve unit is initially directed to one end of the cylinder and thereafter is caused by jet airstreams created by reciprocation of the piston to be applied alternately to opposite ends of the piston cylinder.

United States Patent lnventor Paul Bilodeau Utica, N.'Y.

App]. No. 850,422

Filed Aug. 15, 1969 Patented Feb. 23, 1971 Assignee Chicago Pneumatic Tool Company New York, N.Y.

PNEUMATIC PERCUSSIVE TOOL HAVING A FLUIDIC CONTROL VALVE 8 Claims, 4 Drawing Figs.

us. Cl 173/135;

rm. Cl 1323b 45/00 Field ol'Search..... 173/135,

[56] References Cited UNITED STATES PATENTS 3,241,622 3/1966 Ottosson et a1. 173/170 3,396,631 8/1968 Woodward t 91/3 3,448,481 6/1969 Jones, Jr .1 91/3 Primary Examiner-James A. Leppink Attorney-Stephen J. Rudy BACKGROUND OF THE INVENTION This invention is concerned with a pneumatically powered percussive tool in which a fluidic valve unit is incorporated so as to cause alternate application of operating air to opposite ends of a piston hammer.

Pneumatic Percussive tools are known as having windblown' valves. These are mechanical structures having a slidable valve element which is caused, in response to reciprocation of the piston hammer, to oscillate back and forth so as to cause alternate flow of operating air to opposite ends of the piston cylinder. The moving parts of windblown' valves are subject to wear and tear, and require replacement in due time. On the other hand, fluidic valve unit has only passages and no moving parts; consequently, it is longer lasting than known mechanical valves.

Accordingly, the general objective of this invention is to provide a pneumatically powered percussive toolhaving a fluidic air control value unit incorporated therein.

BRlEF DESCRIPTION or Tris DRAWING In the accompanying drawing: FIG. 1 is a vertical section through a pneumatically powered percussive demolition tool embodying the invention;

YY ture being shown as is required to show the relocation of the trip ports.

DESCRIPTION OF PREFERRED EMBODIMENTS 'In FIGS. 1-3 of the drawing is shown a pneumatically powered percussive tool of the pavement breaker type, having an elongated housing providing a piston cylinder 1 l in which the usual piston hammer I2 is pneumatically reciprocable to pound an anvil 13 against a work steel 14. The latter is axially slidable in a bushing 15 and projects at its work end (not shown) through an open front end of the housing. During operation of the tool, the anvil normally has the elevated position shown. I

The housing includes a backhead portion 19 provided with the usual laterally extending handleportions 21 adapted to be manually gripped by the operator. The backhead is detachably bolted to the upper end of the housing. A manually operable throttle valve 22 controls flow of live air from a supply line 23 to a main inlet passage 24. The inlet passage communicates through a fluidic valve unit with opposite ends of the piston cylinder. The valve unit is effective to cause inlet air to flow alternately to opposite ends of the piston cylinder to reciprocate the piston. The valve unit is separable from the housing and is releasably retained therein. 1! is defined by means of a plurality of passages, as will be described herein, formed in a body structure or block 25. j

Here, the valve block 25 is of circular form; and is retained in a fixed position in a complementary recess 26 of the backhead. The marginal area of the underface 27 of the valve block abuts an annular shoulder 28 formed about the upper end of the piston cylinder; and is held seated thereon in a fixed position by means of a heavy overhead spring 9. In the valve block are two cutlet passages 29 AND 31 WHICH CON- VERGE TOWARD ONE ANOTHER AND INTERSECT WITHIN THE BLOCK TO FORM A COMMON TAPERED REACTION CHAMBER 0-. A jet inlet passage 32 connects the narrower end of chamber 31 through the periphery of the lock with the main inlet passage 24. The outlet passage 29 connects the chamber with a feed port 33 which opens piston cylinder. The other outlet passage 30 extends through the periphery of the block and connects with a passage 34 which leads through the housing wall and opens by means of a second feed port 35 into the lower end of the piston cylinder below ton. A pair of jet trip passages 36 and 37 branch off laterally in opposite directions from the point of juncture of the common chamber 31 with the jet inlet passage 32. The trip passage 36 opens into a larger diameter passage 38 which ex tends through the periphery of the block and connects with a housing wall passage 39. The latter opens by means of a trip port 40 into the piston cylinder at a point a little below the exhaust port 41 of the cylinder. The other trip passage 37 opens into a larger diametr passage 42 which extends through the periphery of the block and connects with a housing wall passage 43. The latter opens by means of a trip port 44 into the piston cylinder a little above the exhaust port 41.

Operation of the tool is as follows: Following opening of the throttle valve, a jetstream of live air issues from the jet inlet passage 32 into the common chamber 31 wherein it impinges the oppositely located ridge or splitter '45 that divides the outlet passages 29 and 30 from one another. Various pressures developed by the jet'stream in entering the common chamber react according to known principles to cause the jetstream to attach itself to the wall of one of the outlet passages. If in the condition of the tool, as in FIGS.- l-3, the jetstream initially attaches itself to the wall of the outlet passage 30, it will flow through the housing passage 34 to the feed port 35 at the lower end of the piston cylinder to drive the piston upwardly away from the anvil 13 to initiate the piston cycle. If in the FIGS. I3 condition of the tool the jetstream initially attaches itself to the other outlet passage 29, it will flow through feed port 33 into the top end of the piston cylinder above the piston, which area is at this time open to the exhaust port 41.

In this situation, a saturation point will rapidly develop in the outlet passage 29 causing some of the inlet jetstream to spill over into the other outlet passage 30. The spilled over air flowing through port 35 to the lower end of the piston cylinder will be adequate to force the piston upwardly to initiate the piston cycle. If in a further condition of the tool, the piston is centered over the exhaust port 41, the piston cycle will be initiated by live air initially entering through port 35 to the lower end of the piston cylinder.

Let it be assumed that the piston cycle has been initiated and the piston is moving upwardly toward the handle end of the tool under force of live air issuing out of feed port 35. As the striking face 46 of the piston clears the lower trip port 40, the live air below the piston passes through the lower trip port 40, passages 39 and 38 to the jet trip passage 36. It jets from passage 36 against the inlet jetstream to switch the latter into the other outlet passage 29 from where the stream will flow through feed port 33 to the top end of the'piston cylinder. At about the time live air is entering the top end of the cylinder, the piston will have moved above the exhaust port 41 to a position short of the top end of the cylinder, and the spent air below the piston will have exhausted through port 41. The piston is then driven downwardly to strike the anvil under the force of live air entering the top end of the cylinder through feed port 33. As the top face of the piston moves below the upper trip port 44, passages 43 and 38 to the jet trip passage 37. It jets from the latter to switch the inlet jetstream back to through the bottom face 27 of the block into the top end of the outlet passage 30. In the meanwhile, the piston will have cleared exhaust port 41 to strike the anvil and to allow exhaust of spent air from above the piston. Live air will then enter the lower end of the cylinder through feed port 35 to recycle the piston upwardly at about the time that the piston strikes the anvil. The switching of the inlet air through the fluidic valve unit alternately to opposite ends of the cylinder to reciprocate the piston will continue automatically until the operator releases the throttle valve to closed condition.

The location of trip ports 40 and 44 in the FIG. 1 structure of the tool permits live air to effect the tripping of the jet inlet stream from one branch outlet to the other. FIG. 4 presents a modification of the tool which is the same as the FIG. I structure except that the trip ports 40a and 44a have been located relatively close to the related feed ports 35 and 33. In this modification, the air that is compressed in the cylinder 11 by the reciprocating piston 12 alternately through ports 40a and 44a operates through the jet trip passages 36 and 37 to cause shifting of the inlet air stream alternately to the outlet passages 29 and 30 leading to the opposite ends of the piston cylinder.

lclaim:

l. The combination in a percussive tool of a housing having a piston cylinder in which a piston hammer is pneumatically reciprocable to pound an anvil against a work steel, and a separable fluidic valve unit having a fixed position in the housing controlling flow of live inlet air alternately to opposite ends of the cylinder to cause reciprocation of the piston hammer, together with a backhead detachably fixed to the housing having a recess overlying a top end of the cylinder in which recess the body of the valve unit is releasably retained; wherein the housing has an annular shoulder recessed about the top end of the cylinder, the body of the valve unit is circular in form and has a flat bottom face seated about its marginal area upon the shoulder, and there being a spring seated in the recess above a top face of the body of the valve unit retaining the valve unit seated upon the shoulder.

2. The combination in a percussive tool of a housing having a piston cylinder in which a piston hammer is pneumatically reciprocable to pound an anvil against a work steel, and a separable fluidic valve unit that has a fixed position in the housing controlling flow of live inlet air alternately to opposite ends of the cylinder to cause reciprocation of the piston hammer and comprises a body structure having a common chamber, a pair of outlet passages forked from one end of the chamber, a jet inlet passage opening into an opposite end of the chamber, one of the outlet passages opening through a bottom face of the body structure, the other outlet passage opening through a sidewall of the body structure, and a pair of jet trip passages extending laterally in opposite directions in the body structure from the point of juncture of the jet inlet passage with the chamber; wherein the common chamber is tapered, the outlet passages are forked from a wider end of the chamber, there being a narrow ridge wall portion of the chamber separating the forking outlet passages, an the opening of the jet inlet passage is into the narrower end of the chamber in opposed relation to the ridge wall.

3. The combination as in claim 2, wherein the housing has a passage connecting one of the outlet passages with a lower end of the cylinder, and the opening of the other outlet passage through the bottom face of the body structure connects directly with a top end of the cylinder.

4. The combination as in claim 3, wherein an exhaust port from the cylinder is located intermediately of the ends of the cylinder.

5. The combination as in claim 4, wherein one of the jet trip passages connects with a passage of larger diameter leading through the housing wall into the-cylinder at a first point below the exhaust port, and the other jet trip passage connects with a passage of larger diameter leading through the housing wall into the cylinder at a second point above the exhaust port.

6. The combination as in claim 5, wherein the first point is located above and in close proximity to the connection of the one outlet passage with the lower end of the cylinder, and the second point is located below and in close proximity to the top end of the cylinder.

7. In a percussive tool including a housing providing a piston cylinder in which a piston hammer is pneumatically reciprocable to pound an anvil against a work steel, the housing including a recess above the cylinder; a fiuidic valve unit comprising a block retained in the recess having a tapered chamber, a pair of outlet passages forked from the wider end of the chamber, and inlet jet passage connecting with the narrower end of the chamber, and a pair of trip jet passages extending laterally in opposite directions from the point of juncture of the inlet jet passage with the chamber; the cylinder having an exhaust port located intermediately of its ends; the housing having a passage connecting one of the outlet passages with a lower end of the cylinder, the other outlet passage having a connection with the top end of the cylinder; a passage connecting one of the trip passages with the cylinder at a point above the exhaust port; and another passage connecting the other trip passage with the cylinder at a point below the exhaust port.

8. In a percussive too] including a housing providing a piston cylinder in which a piston hammer is pneumatically reciprocable, the housing including a recess above the cylinder; a fluidic valve unit comprising a block retained in the recess having a tapered chamber, a pair of outlet passages forked from the wider end of the chamber, an inlet jet passage connecting with the narrower end of the chamber, and a pair of trip jet passages extending laterally in opposite directions from the point of juncture of the inlet jet passage with the chamber; the cylinder having an exhaust port located intermediately of its ends; the housing having a passage connecting one of the outlet passages with a lower end of the cylinder, the other outlet passage having a connection with the top end of the cylinder; a passage connecting one of the trip passages with the cylinder at a point above the exhaust port; and another passage connecting the other trip passage with the cylinder at a point below the exhaust port. 

1. The combination in a percussive tool of a housing having a piston cylinder in which a piston hammer is pneumatically reciprocable to pound an anvil against a work steel, and a separable fluidic valve unit having a fixed position in the housing controlling flow of live inlet air alternately to opposite ends of the cylinder to cause reciprocation of the piston hammer, together with a backhead detachably fixed to the housing having a recess overlying a top end of the cylinder in which recess the body of the valve unit is releasably retained; wherein the housing has an annular shoulder recessed about the top end of the cylinder, the body of the valve unit is circular in form and has a flat bottom face seated about its marginal area upon the shoulder, and there being a spring seated in the recess above a top face of the body of the valve unit retaining the valve unit seated upon the shoulder.
 2. The combination in a percussive tool of a housing having a piston cylinder in which a piston hammer is pneumatically reciprocable to pound an anvil against a work steel, and a separable fluidic valve unit that has a fixed position in the housing controlling flow of live inlet air alternately to opposite ends of the cylinder to cause reciprocation of the piston hammer and comprises a body structure having a common chamber, a pair of outlet passages forked from one end of the chamber, a jet inlet passage opening into an opposite end of the chamber, one of the outlet passages opening through a bottom face of the body structure, the other outlet passage opening through a sidewall of the body structure, and a pair of jet trip passages extending laterally in opposite directions in the body structure from the point of juncture of the jet inlet passage with the chamber; wherein the common chamber is tapered, the outlet passages are forked from a wider end of the chamber, there being a narrow ridge wall portion of the chamber separating the forking outlet passages, an the opening of the jet inlet passage is into the narrower end of the chamber in opposed relation to the ridge wall.
 3. The combination as in claim 2, wherein the housing has a passage connecting one of the outlet passages with a lower end of the cylinder, and the opening of the other outlEt passage through the bottom face of the body structure connects directly with a top end of the cylinder.
 4. The combination as in claim 3, wherein an exhaust port from the cylinder is located intermediately of the ends of the cylinder.
 5. The combination as in claim 4, wherein one of the jet trip passages connects with a passage of larger diameter leading through the housing wall into the cylinder at a first point below the exhaust port, and the other jet trip passage connects with a passage of larger diameter leading through the housing wall into the cylinder at a second point above the exhaust port.
 6. The combination as in claim 5, wherein the first point is located above and in close proximity to the connection of the one outlet passage with the lower end of the cylinder, and the second point is located below and in close proximity to the top end of the cylinder.
 7. In a percussive tool including a housing providing a piston cylinder in which a piston hammer is pneumatically reciprocable to pound an anvil against a work steel, the housing including a recess above the cylinder; a fluidic valve unit comprising a block retained in the recess having a tapered chamber, a pair of outlet passages forked from the wider end of the chamber, and inlet jet passage connecting with the narrower end of the chamber, and a pair of trip jet passages extending laterally in opposite directions from the point of juncture of the inlet jet passage with the chamber; the cylinder having an exhaust port located intermediately of its ends; the housing having a passage connecting one of the outlet passages with a lower end of the cylinder, the other outlet passage having a connection with the top end of the cylinder; a passage connecting one of the trip passages with the cylinder at a point above the exhaust port; and another passage connecting the other trip passage with the cylinder at a point below the exhaust port.
 8. In a percussive tool including a housing providing a piston cylinder in which a piston hammer is pneumatically reciprocable, the housing including a recess above the cylinder; a fluidic valve unit comprising a block retained in the recess having a tapered chamber, a pair of outlet passages forked from the wider end of the chamber, an inlet jet passage connecting with the narrower end of the chamber, and a pair of trip jet passages extending laterally in opposite directions from the point of juncture of the inlet jet passage with the chamber; the cylinder having an exhaust port located intermediately of its ends; the housing having a passage connecting one of the outlet passages with a lower end of the cylinder, the other outlet passage having a connection with the top end of the cylinder; a passage connecting one of the trip passages with the cylinder at a point above the exhaust port; and another passage connecting the other trip passage with the cylinder at a point below the exhaust port. 